Processes based on plasma of reactive gases are adopted widely in the manufacturing of LSIs, LCDs, etc. Particularly, the dry etching technique using plasma is an indispensable fundamental technique for the manufacturing processes of LSIs, LCDs, etc.
On the other hand, as the size of substrates used for the fabrication of LSIs, LCDs, etc. increases, it is required to generate plasma uniformly over a wide area. It is also required for the dry etching technique and the embedding technique for thin film formation to control plasma generation and ion energy in the plasma independently.
The present applicant has disclosed in Japanese patent publication JP-A-Hei-6-104098 a plasma processing apparatus which is capable of generating plasma uniformly over a wide area and controlling the ion energy.
FIG. 1 is a brief vertical cross-sectional view of this plasma processing apparatus.
In the apparatus, a reaction room 12 has a microwave window 14 at the top, and a dielectric plate 32 for propagating the microwave is laid over the microwave window 14. A Radio frequency (RF) power source 28 is connected to a sample stage 15, which confronts a counter electrode 41 which is attached on the lower surface of the microwave window 14 by being grounded electrically.
FIG. 2 is a top view of an example of the counter electrode 41.
The counter electrode 41, which is made of metal such as aluminum, has microwave introduction holes 41a for introducing the microwave into the reaction room 12.
In the apparatus, the microwave is propagated flatly in the dielectric plate 32. Accordingly, it is possible for the apparatus to generate uniform plasma in a wide area by having a large dielectric plate 32 and a large microwave window 14.
Based on the disposition of the counter electrode 41 on the lower surface of the microwave window 14, it is possible for the apparatus, in the case of applying an RF voltage to the sample stage 15, to stabilize the electrical circuit including the sample stage, plasma and counter electrode, and generate a stable bias voltage on the surface of a sample S. Consequently, it is possible to control stably the acceleration of ion (ion energy) in the plasma by varying the bias voltage.
The apparatus is designed to generate plasma mainly by using the microwave and control the ion energy mainly by using the RF voltage applied to the sample stage. Accordingly, it is possible to control plasma generation and ion energy independently.
However, the apparatus of the above-mentioned structure has its counter electrode located immediately above the sample. Because of this, the deposit is created in plasma and sticks to the counter electrode and the counter electrode itself is liable to be sputtered by the plasma and stick to the sample S. As a result, the apparatus is liable to suffer from the sticking of particles to the sample and also from metallic contamination.
The present invention is intended to resolve the foregoing problems, and its object is to provide a plasma processing apparatus and plasma processing method capable of reducing the sticking of particles to the sample and metallic contamination.